QUATERNARY SURFICIAL MAPPING OF CENTRAL PANAMINT VALLEY TO EVALUATE PALEOSEISMIC EVIDENCE FOR MULTI-FAULT RUPTURE, EASTERN CALIFORNIA SHEAR ZONE

We present new, high-resolution tectonogeomorphic surficial mapping of Quaternary alluvium and fault scarps in the central Panamint Valley transtensional relay (PVTR), Eastern California Shear Zone. This 250 km² map compiles newly mapped alluvial fans, lake deposits, and faults in the ~40 km² between the Ash Hill and Panamint faults to evaluate how strain may be transferred between two fault systems. We completed field and remote mapping of this area between October 2021 and May 2022, at a resolution of 1:12 k and 1:4 k, using GeoEye imagery base maps and existing NCALM 0.5 m airborne lidar DEMs. As existing lidar is unable to resolve small (0.5 – 1m) fault offsets and fan surface morphology, we additionally collected drone-based photogrammetry and produced 5 cm structure-from-motion (SfM) digital surface models (DSMs) to aid in mapping and fault offset analysis. SfM surveys were collected using a DJI Phantom IV drone with a 12.4-megapixel camera, at a height of 75 - 475 m above the ground surface, over 200 m² swaths. Mapping included the development of a high-resolution fan chronology consisting of ten generations of late Quaternary alluvial deposits, based on changes in bar and swale morphology, weathering, and desert pavement development. We further date mapped deposits using post-infrared feldspar infrared-stimulated luminescence, and quantify kinematics by measuring cumulative displacement in the field and from DSMs. Using our fan chronology, inset and burial relationships, IRSL dated deposits, and relationships to spring and lake deposits in the valley, we correlate Quaternary deposits across three fault systems.

These new map data yield the following results: 1) The PVTR has experienced four earthquakes in the last ~4 ka, with each event rupturing different sub-segments of the PVTR; 2) The timing of these earthquakes overlap with rupture timing on the Ash Hill and Panamint faults and each event is bracketed by morphologically similar alluvial fans; 3) Displacement magnitude per event and slip kinematics in the PVTR are similar to that of the Ash Hill fault, but fault orientations are similar to the Panamint fault. Our mapping thus provides new evidence that this complex fault zone may act as a relay for strain transfer between the Ash Hill and Panamint faults over multiple earthquake cycles.